Modern automobile body shapes are distinguished by relatively large window areas. Because of strong sunlight, the large window areas result in considerable heat generation in the interior of the vehicle and, in connection with vehicles with air conditioning, this major heat generation results in a considerable use of energy in order to counteract the heating effects on the vehicle.
For this reason, motor vehicles are increasingly equipped with windup window shades. A rear window windup shade is known from DE 36 12 165 A1, which has a windup shaft which is rotatably seated in a base. The base is located on or underneath the rear window shelf. The window shade web of the rear window windup shade is pulled out from the rear window shelf in the direction toward the rear edge of the roof. The windup shaft, which is rotatably seated in the base and is biased by a spring drive in the windup direction, is used for storing the unused part of the window shade web. A traction rail is fastened on the edge of the window shade web remote from the windup shaft. With the aid of second pivot levers, the traction rail is transferred from a position in which it directly adjoins the windup roller into a position in which the window shade web covers nearly the entire window. For this purpose the pivot levers are essentially rigid in the direction perpendicular to that plane in which they move in the course of the retraction and extension of the windup shade.
Only two settings for light penetration through the rear window are possible with the known blind. In one state light can enter unhampered through the rear window, because the windup shade is completely wound on the windup roller, while in the other state a reduction occurs in accordance with the permeability to light of the windup shade web.
It is furthermore known to attach two guide rails laterally next to the window, in which the end of the traction rod of the window shade web is guided. The length of the traction rod is adjustable in order to be able to accommodate various window widths. Actuation takes place by means of the thrust members running in the guide rails.
Only two states are possible here, too, namely the unhampered entry of light or reduction in accordance with the reduction effects of the windup shade web.
Based on the foregoing it is the object of the invention to create a windup window shade for motor vehicles, which allows a total of three operational states, wherein a different reduction of the entry of light over the entire window area can be set.
It is possible by means of the windup window shade of the invention to achieve at least two additional shading states in addition to the completely unaffected light entry.
These different states can be achieved with window shade means comprising two window shade webs, which can be extended alternatively or simultaneously.
In one of the embodiments, the window shade means of the windup window shades are connected with each other along an edge, so that either no window shade web at all or one or the other window shade web can be pulled in front of the window. The other variation provides two window shade webs, which are separate from each other and can be actuated independently of each other to the greatest extent.
One of the window shade webs can be made of a woven material or a perforated foil in order to permit light into the car interior in a metered manner. The other window shade web can be completely dark, or for example also be provided with a metallized coating in order to completely block the entry of infrared light into the interior of the car. Moreover, the opaque window shade web has the advantage of preventing a view of the car interior, which is advantageous in particular in parked vehicles.
Guide means are assigned to the windup window shade means for maintaining the extended state. These guide means can consist of guide rails or pivot levers. The variation with the guide rails makes it possible to cover the windows to the greatest extent. To this end two guide rails extend next to the edges of the window, which follow the contours of the window. At least one traction rod, sometimes called a traction rail herein, on which an edge of the respective window shade web is fastened, runs in these guide rails.
With the embodiment with two independent window shade webs, the guide rails have two guide grooves on each side, wherein one guide groove of each guide rail is assigned to the one window shade web, and the other to the other window shade web.
So that the traction rails can follow the trapezoidal or converging shape, the respective traction rail is embodied to be adjustable in length.
The retraction and extension of the respective window shade web can take place in that the respective traction rail is driven by an electric motor. Thrust or pressure members are provided for this, which are put in motion by the motor and move the ends of the respective traction rail in the guide groove. The window shade webs are suitably biased in the retraction direction by means of spring drives.
The variation with two window shade webs can also be controlled very simply with only a single motor. To this end, one end of the linearly-shaped pressure member is coupled with the traction rail of the one window shade web, and the other end with the traction rail of the other window shade web. In other words, the return strand of the thrust member on the part of one window shade web is at the same time the driving strand on the part of the other window shade web. Cross-coupling is achieved in this way, which provides that both window shade webs are retracted in the center position of the thrust member. If the thrust member is extended in the one direction, one of the window shade webs is extended, while during the extension in the opposite direction the other window shade web is pulled out. In the center position both window shade webs are retracted.
The thrust or pressure members are preferably approximately cylindrical structures, which are provided with teeth on the exterior. Because of the approximately dynamically balanced design it is possible to overcome curved guides easily. Such a thrust member is obtained if an essentially cylindrical core is provided with a helically extending rib. Such thrust members are flexible shafts known in actual use under the commercial designation SUFLEX(trademark) shafts.
Actuation of the individual window shade webs becomes simple if an individual windup shaft is provided for each window shade web. Each one of the windup shafts is biased in the retracting direction of the respective window shade web by its own spring drive.
To prevent the skewed pulling of the window shade web, which results in obliquely extending waves in the window shade web, it is practical to seat the respective windup shaft in a hoop, which itself is also pivotable in respect to the drive direction, or to the guide rails, namely around an axis extending perpendicularly in respect to the axis of the windup shaft. An offset, which is created when the thrust members in the respective guide rails are not exactly at the same effective height, can be compensated by means of such seating. In this case effective height is understood to be the effective distance of the end of the thrust member from the axis of the windup shaft. Different effective heights would mean that on the one edge the traction rail of the respective window shade web would be forced to be at a greater effective distance from the windup shaft than on the other edge, because of which the window shade web is deformed and tends to develop folds.
As already expressed at the outset, the option of achieving different grades of shade can also be created with the aid of pivot levers. The pivot levers can either be simple rigid levers or toggle levers. In either case, one end of the levers is seated pivotable around shafts which extend at right angles in respect to the axis of the windup shaft.
A traction rod, on which a further windup shaft is rotatably seated, is moved away from or toward the windup shaft with the aid of the pivot levers. In this case the windup window shade means consist of two window shade webs, fastened one behind the other in the direction of movement which, similar to a film in a camera, are moved back and forth between the two windup shafts. In the last mentioned option it is necessary for the leading window shade web to have a rectangular shape, so that it can be completely wound on the respective windup shaft seated on the traction rod. Because of the trapezoid window geometry, the traction rod as a rule is considerably shorter than would correspond to the width of the window in the lower area. Only the second window shade web can be matched to the trapezoidal window geometry.